渲染顶点缓冲区阵列OpenGL ES2

Question

我正在尝试渲染一系列VBO，但结果不对。当我第一次使用GLPaint（OpenGLES v2）设置绘制它们时，我将它们保存到数组中。如果您想帮助我，这是我的示例项目。 https://drive.google.com/file/d/0B0pG5vRVzBTzUTZPYWNoenhkcWs/edit?usp=sharing

////// Store VBOs when drawing this is done in renderLineFromPoint (from GLPaint)
- (void) renderLineFromPoint:(CGPoint)start toPoint:(CGPoint)end
{

static GLfloat*     vertexBuffer = NULL;
static NSUInteger   vertexMax = 64;
NSUInteger          vertexCount = 0,
count,
i;

[EAGLContext setCurrentContext:context];
glBindFramebuffer(GL_FRAMEBUFFER, viewFramebuffer);

// Convert locations from Points to Pixels
CGFloat scale = self.contentScaleFactor;
start.x *= scale;
start.y *= scale;
end.x *= scale;
end.y *= scale;

// Allocate vertex array buffer
if(vertexBuffer == NULL)
    vertexBuffer = malloc(vertexMax * 2 * sizeof(GLfloat));

// Add points to the buffer so there are drawing points every X pixels
count = MAX(ceilf(sqrtf((end.x - start.x) * (end.x - start.x) + (end.y - start.y) * (end.y - start.y)) / kBrushPixelStep), 1);

for(i = 0; i < count; ++i)
{
    if(vertexCount == vertexMax)
    {
        vertexMax = 2 * vertexMax;
        vertexBuffer = realloc(vertexBuffer, vertexMax * 2 * sizeof(GLfloat));
    }

    vertexBuffer[2 * vertexCount + 0] = start.x + (end.x - start.x) * ((GLfloat)i / (GLfloat)count);
    vertexBuffer[2 * vertexCount + 1] = start.y + (end.y - start.y) * ((GLfloat)i / (GLfloat)count);
    vertexCount += 1;
}

glBindBuffer(GL_ARRAY_BUFFER, vboId);
glBufferData(GL_ARRAY_BUFFER, vertexCount*2*sizeof(GLfloat), vertexBuffer, GL_DYNAMIC_DRAW);

glEnableVertexAttribArray(ATTRIB_VERTEX);
glVertexAttribPointer(ATTRIB_VERTEX, 2, GL_FLOAT, GL_FALSE, 0, 0);

// Render the vertex array
glVertexPointer(2, GL_FLOAT, 0, vertexBuffer);
glDrawArrays(GL_POINTS, 0, vertexCount);

// Display the buffer
glBindRenderbuffer(GL_RENDERBUFFER, viewRenderbuffer);
[context presentRenderbuffer:GL_RENDERBUFFER];

// Store VBO for undo
VBOHolder *vboHolder = [[VBOHolder alloc]init];
vboHolder.vertexCount = vertexCount;
vboHolder.vbo = vertexBuffer;
[vboHolderArray addObject:vboHolder];

}

////// Here is the problem: I clear the screen and then try to re-render the VBOs
-(void)renderSavedVertexBufferes
{

  for (VBOHolderModel *vboh in vboHolderArray)
  {
    if (vboh.vertexCount == 0)
    {
        continue;
    }

    NSUInteger vertexCount = vboh.vertexCount;

    glBindBuffer(GL_ARRAY_BUFFER, vboId);
    glBufferData(GL_ARRAY_BUFFER, vertexCount*2*sizeof(GLfloat), vboh.vbo, GL_DYNAMIC_DRAW);

    glEnableVertexAttribArray(ATTRIB_VERTEX);
    glVertexAttribPointer(ATTRIB_VERTEX, 2, GL_FLOAT, GL_FALSE, 0, 0);

    // Render the vertex array
    glVertexPointer(2, GL_FLOAT, 0, vboh.vbo);
    glDrawArrays(GL_POINTS, 0, vertexCount);

    // Display the buffer
    glBindRenderbuffer(GL_RENDERBUFFER, viewRenderbuffer);
    [context presentRenderbuffer:GL_RENDERBUFFER];

  }
}


////// VBOHolderModel looks like this, it wraps the vbo so it can be put in NSMutableArray
@interface VBOHolderModel : NSObject
{
   GLfloat *vbo;
   NSUInteger vertexCount;

}

它基本上是一个撤消...当按下撤消它应该只删除3，因为它是最后一个笔划，但它将全部删除并绘制第二个图像中显示的点。

Answer 1

我在下面的行中找到了这个问题的答案

// Allocate vertex array buffer
if(vertexBuffer == NULL)
vertexBuffer = malloc(vertexMax * 2 * sizeof(GLfloat));

问题是存储的顶点阵列都是一样的！当vertexBuffer为null时，它只在init上分配一次内存。其他一些代码有所改变，如果你想要更新，请告诉我。